Sea fog is funny stuff. It comes rolling in off the sea and then decides to stop, and there’s a sharply defined edge to where it starts and stops. I’ve been driving down the seafront in Hastings on the seaward side of the road in thick fog, while being able to see that the cars passing on the other side of the road are still in bright sunlight.

The first time I visited San Francisco I was lucky enough to be sifting on top of one of the Twin Peaks at dusk, just as the fog started rolling in from the Pacific. It was quite magical – the fog rolled over the Sunset district, up the escarpment to the peaks, and then divided into three as it rolled around the two summits, and flowed down the other side to the Castro. In five minutes I was sitting under a clear starry sky on a small island in a sea of clouds, with just a few other islands and telecoms towers poking out of the mist. Jones is doing her best impersonation of the Twin Peaks in the last frame.